Voltage converters such as DC-DC converters come in two forms. When an input voltage is to be stepped up in voltage by the converter, a boost or step-up configuration is provided. When the input voltage needs to be stepped down to a lower voltage by the converter, a buck converter is provided. Thus, a buck converter is a step-down DC-DC converter. Its design is similar to the step-up boost converter, and like the boost converter, it is a switched-mode power supply that employs switches (e.g., a transistor and a diode), an inductor and a capacitor. Switching converters can be quite efficient (e.g., 95% or higher for integrated circuits), making them useful for tasks such as converting the main voltage in a computer (e.g., 12 V in a desktop, 12-24 V in a laptop) down to the 0.8-1.8 volts needed by the processor.
Inductive DC-DC Converters running with constant switching frequency have a principle problem that they run with low power efficiency at light loads due to high (constant) switching losses that mainly depend on the switching frequency. To overcome this, designers employ skip-or burst modes to reduce the number of switching cycles at light loads. The problem with these operating modes is that they need additional sense and control circuits in addition to the fact that they generate high ripple voltages on the output.